Safety fuel system for heaters



Sept. 18, G. w. ALLEN I SAFETY FUEL SYSTEM FOR HEATERS 3 Sheets-Sheet 1Filed Sept. 5, 1943 ENEINE CA RB URE TOR SAFETY VAL VE Patented Sept.18, 1951 SAFETY FUEL SYSTEM FOR HEATERS George W: Allen, Indianapolis,Ind., assignor to Stewart-Warner Corporation, Chicago, Ill., acorporation of Virginia Application September 3, 1948, Serial No. 47,567

(Cl. I5828) 13 Claims.

The present invention relates to safety fuel systems and moreparticularly to a liquid fuel system for use with heaters, particularlybut not necessarily of the small internal combustion type.

One of the objects of the present invention is to provide a simple butinherently safe fuel system for use with heaters or other fuel consumingdevices.

Still another object is to provide a fuel system having the abovecharacteristics and in which a quantity of fuel is isolated for startingpurposes and this quantity of fuel is supplemented by an additional fuelsupply connection to be used only in the event that the fuel consumingdevice operates promptly.

Still another object is to provide a fuel system having the givencharacteristics and in which the device functions completelyautomatically.

Still another object is to provide a fuel system having the abovecharacteristics and which is not sensitive to vibratory forces or toorientation.

Other objects and advantages will become apparent from the followingdescription of several similar embodiments of my invention, theinvention being illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a fuel system in anautomotive vehicle which is intended to supply both the vehicle engineand the combustion heater with fuel and which includes the safety deviceof the present invention;

Fig. 2 is a top view of the principal mechanical safety element used inthe system of Fig. 1;

Fig. 3 is a vertical sectional view and may be considered as taken inthe direction of the arrows substantially along the line 3-3 of Fig. 2;

Figs. 4 to 7 are electrical diagrams showing alternative circuitarrangements for controlling and operating the heater and safety deviceof Figs. 1 to 3.

Referring to Fig. 1 of the drawings it will be seen that a fuel tank Iwhich may be considered as the fuel tank of an automobile is connectedby a fuel line [2 to a filter i4 and thence to a pump 16 which isconnected on its outlet side by a pipe I8 and branch 23 to the vehicleengine carburetor 22. This much of the system may be considered asconventional in an automotive vehicle and is normally present forsupplying filtered fuel under pressure from the vehicle tank to theengine carburetor. The pipe It also leads to the safety device indicatedgenerally by the numeral 24 and which comprises one of the principalelements of the present invention. This 2 safety device is connected onits outlet side with a pipe 26 which leads to a magnetic shut-off valve28 of conventional design and thence to a vehicle heater 30 of thecombustion type. This heater may be of the type illustrated anddescribed in copending application filed June 1 1946, for "Heaters andwhich has been given Serial No. 676,776, now Pat. No. 2,507,081, grantedMay 9, 1950.

Referring to Figs. 2 and 3 of the drawings the safety device of thepresent invention includes a base member 32 and a cover member 34, bothof which may be formed as sand castings or die castings or the like.These two members are generally cup shaped and circular in outline andare secured together in face to face relation by a plurality of screws36 spaced around the periphery. The members when together ericlose aspace or chamber which is divided by a flexible diaphragm 38. Thisdiaphragm is secured around its edges between the mating faces of theupper and lower members 34 and 32and acts as a gasket to seal thechamber as well as a flexible member for dividing the space within thecastings into a lower chamber 40 and an upper chamber 42.

A rivet 46 extends through the center of the diaphragm from the lowersurface thereof and passes through a washer 48 above the diaphragm, thestem of the rivet being peened over to fix the rivet in place and form aleak-proof structure. The lower end of this rivet forms a spring seatwhich bears against the upper end of a coil spring 50, the lower end ofwhich is seated in a socket 52 formed in the base casting 32. Thisspring is comparatively light in its action but has sufficient forcetourge the diaphragm 38 into its uppermost position with the top end ofthe rivet 46 against the inside surface of the cover member 34. Acomparatively light hydraulic pressure in the upper chamber 42 will urgethe diaphragm 38 downwardl while compressing the spring until the lowersurface of the diaphragm closely follows the contour of the insidesurface of the base member 32. The movement of the diaphragm from sideto side, therefore, is such that when the diaphragm is in the uppermostposition the lower chamber 40 is large while the upper chamber 42 issmall. Conversely, when the diaphragm is in the lower position the upperchamber 42 is large while the lower chamber 40 is small.

The upper casting 34 is formed to provide an inlet fitting 54 which isconnected to the pipe l8 previously mentioned. Thus, fuel under pressurein the pipe IB is in communication with the upper chamber 42. Similarly,an outlet fitting 56 is formed as a portion of the lower member 32 andcommunicates by way of a passage 68 with the lower chamber 40. Thisfitting 56 is connected to the outlet line 26 which leads to themagnetic shut-off valve 28.

A magnetic by-pass valve 60 is mounted upon the cover member 34. Thismagnetic valve has a plunger 62 which in the downward position acts toclose a valve seat 64 formed as a portion of the cover 34. When themagnetic valve is energized, the plunger 62 is lifted to the positionshown in Fig. 3, thereby uncovering the valve seat 64 so as to permit aflow of fuel from the upper chamber 42 by way of a'passage 66 into anannular chamber 68 surrounding the valve members 62 and 64 and thencethrough the valve seat 64 and into drilled intersecting passages I and12, the latter of which communicates with the outlet fitting 56.Conveniently, the passages 66, I0 and I2, the annular chamber 68 and thevalve seat 64 may all be formed by machining the cover casting 34.

From the above description of the device of Figs. 2 and 3 it will beseen that fuel under pressure may flow into the upper chamber 42whenever the pumpl6'is operated, that the lower chamber 48 is incommunication with the outlet pipe 26 at all times and that whenever thema netic valve 60 is energized fuel will flow from the upper chamber 42to the lower chamber 40, in other words, from the inlet fitting 54 tothe outlet fitting 56. 'On the other hand, however, when the magneticvalve 60 is de-energized there is no communication between the upper andlower chamber 42 and 40 or between the inlet and outlet fittings 54 and56.

Fig. 4 illustrates an electrical circuit for use with a heater of thetype mentioned when a valve of the above description is included in thefuel circuit. This electricalcircuit may be considered as typical of agroup of circuits suitable for this purpose, four of which will bedescribed.

In Fig. 4 the lead indicated by the numeral I4 is connected to thevehicle ignition switch such that this electric lead is energized onlywhen the vehicle ignition switch is in the on position. This lead I4 isalso connected to a double pole, single throw heater switch 16 which maybe used for placing the heater in and out of operation, provided ofcourse the vehicle ignition switch is in the on position. The lead I4-is connected to both switch contacts 18 and 80 which respectivelyco-operate with contacts 82 and 84. One of these contacts, 84 forinstance, is connected by lead 86 to a thermostatic overheat switch 88which'may be of conventional type and which commonly is mounted upon theheater. This switch is simply a thermostatic normally closed switchwhich opens whenever the temperature of the heater rises sufficientlyhigh to indicate that operation of the heater may become unsafe. Theoutlet side of this overheat switch is connected to one terminal of themagnetic fuel shut-off valve 28, the other terminal of which isgrounded.

It is apparent, therefore, that whenever the vehicle ignition switch isin the on" position and the heater switch I6 is closed, the shut-offfuel valve 28 will be energized and therefore opened, provided of coursethe temperature of the thermostatic overheat switch 88.

The other output contact, 82 for instance, of I the switch I6 isconnected by a lead 90 to a thermostatic igniter switch 92 mounted uponthe heater or otherwise so arranged as to be sensitive either to heatertemperature or to the air temperature on the output side of the heater.This thermostatic switch is of the single pole, double throw type and isso arranged that when the switch 92 is cold the swinging member 94thereof will be against an output contact 96 connected by a lead 98 toone terminal of an igniter I00, the opposite terminal of which isgrounded. Therefore, if the vehicle ignition switch is closed and if theheater switch I6 is also closed and if the heater is cold, the igniterI00 will be energized. If the heater lights properly, the temperaturewill rise sufficiently so that after a comparatively short interval oftime, as an example, half a minute, the temperature of the igniterswitch 92 will rise sufficiently to cause the swinging contact 94 tobreak the circuit with the output contact 96 and to close a circuit tothe other output contact I02 connected by a lead I04 directly to'thevehicle battery.

The lead 90 leading from the contact 82 is also connected by a branchI06 to a combustion air blower motor I08 and a ventilating air blowermotor H0 in parallel. The first of these motors when energized suppliesair to the heater for combustion purposes while the second motor II8drives a ventilating air blower which circulates air through the heaterand to the space to be heated. This branch lead I06 is also connected toone terminal of the by-pass safety valve 60, the other terminal of whichis connected to the swinging member II2 of a single pole, double throwswitch II4. Normally this swinging member of the switch H4 is loaded bya spring or otherwise so that it maintains an electrical circuit with anoutput contact II6 connected by a lead II8 back to contact 96 of theigniter switch 92. The second output contact I28 of the switch I I4 isconnected to ground and a push button I22 is provided which whenmanually actuated urges the switch arm I I2 away from the contact H6 andagainst the contact I20. It is necessary that this push button I22 bemaintained in the depressed position in order to keep the switch in thisposition. As soon as the button is released the switch snaps back to,the position shown in Fig. 4.

This circuit operates in the following manner. Assuming that the vehicleignition switch is in the on" position and that the heater is cold, ifthe heater switch I6 is closed, current will flow by way of contacts and84 and by way of the overheat switch 88 to the fuel shut-off valve 28.

It will be assumed for the purpose of providing a starting point in thedescription that the valve 24 is in the position shown in Fig. 3, thatis, the diaphragm 38 is in the uppermost position and the lower chamber40 is filled with fuel. It should be assumed also that the valve 60 isde-energized and that therefore there is no connection between the upperchamber 42 and the lower chamber 40. Assuming also that the vehicleengine is operating, it will be apparent that the pump I6 will besupplying fuel under pressure. Therefore, fuel flowing into the upperchamber 42 under pressure will urge the diaphragm 38 downwardly, therebydisplacing fuel in the lower chamber 40 out through the passageway 58,fitting 56 and pipe 26 to the fuel shut-off valve 28. Since this valveis energized and therefore open, fuel flows to the heater. Inasmuch asthe spring 50 is quite soft in its action it will be seen that the fuelpressure flowing outwardly through the pipe 26 is substantially as highas the fuel pressure flowing into the upper chamber 42.

Current also flows through the lead 90 to the switch 92 and inasmuch asthis switch is closed, to the contact 96 and then to igniter I00. Thisigniter which conventionally is of the hot wire type immediately startsheating and will reach ignition temperature in a matter of a fewseconds. It will be apparent also that current will be sup plied throughthe branch I06 to the ventilating air blower motor and to the combustionair blower motor I08. Since, however, both terminals of the by-passvalve 60 are connected to the same side of the circuit, that is, thebranch lead I06 connected to one terminal of the by-pass valve is at thesame electrical potential as the lead 98 which is connected through theswitch II4 to the other terminal of the by-pass valve. this valve ofcourse remains closed. Under these conditions the heater should startoperation within a matter of ten seconds or so inasmuch as the igniterwill soon be at ignition temperature and since fuel and combustion airare being supplied in appropriate quantities.

If the heater does not start promptly, the thermostatic igniter' switch92 remains cold and remains in the position shown in Fig. 4. The valve60 therefore remains de-energized and closed. Thus, as soon as fuelflowing into the upper chamber 42 has displaced the diaphragm downwardlyits full distance so as to displace all of the fuel in the chamber 40 tothe heater 30, the heater will cease operation since no more fuel canreach the heater. The preferred size of the chamber 40 depends upon thecharacteristics of the heater and with the heater shown may be such asto provide fuel for approximately two minutes operation. Therefore, ifthe heater does not start promptly the quantity of fuel isolated forstarting purposes in the chamber 40 will become exhausted in about twominutes and the heater will receive no more fuel.

If, on the other hand, the heater does start promptly as it should, thenthe igniter switch 92 will rise in temperature sufficiently to shift thecontact 54 away from the contact 96 and against the contact I02 withinless than a minute. This connects the lead 90 to the contact I02 andthence directly to the vehicle battery with the result that the motorsI08 and I I0 which drive the combustion air blower and the ventilatingair blower no longer depend upon the switch IE or the vehicle ignitionswitch for energization so long as the igniter switch is hot. Also,since the lead 98 is now disconnected from the switch contact 94 currentwill flow through the branch I06 through the by-pass valve 60 throughthe switch H4 and to ground through the igniter I00.

Inasmuch as the lgniter is a low resistance device while the by-passsafety valve 60 has a comparatively high resistance coil, there will besufficient current flow through the by-pass valve 60 to energize thesame and to lift the valve member 62 from the seat 04. The amount ofcurrent flowing through this circuit, however, is not enough to raisethe temperature of the igniter substantially with the result that theigniter cools.

Inasmuch as the valve 60 has been energized the passage therethroughwill be opened, thereby establishing communication between the upperchamber 42 and the lower chamber 40 and between the inlet fitting 54 andthe outlet fitting 56. The vehicle fuel pump therefore continues tosupply fuel to the heater so as to insure continued operation thereof.Also, inasmuch as communication is now established across the two sidesof the diaphragm 38, thereby putting these two sides at substantiallythe same hydraulic pressure, the spring 50 will urge the diaphragm intothe upper position as shown in Fig. 3. The lower chamber 40, therefore,is refilled with fuel in preparation for a new start.

If the heater does not start properly and the fuel within ths chamber 40becomes exhausted, the operator will know that something is wrong andwill either investigate as to the trouble or will take the vehicle to aservice station. When the heater has been put in proper functioningorder again, depressing the button I22 grounds the terminal II2 with theresult that current flows through the by-pass valve 60 so as to energizeand open the same, thereby permitting the chamber 40 to refill under theinriuence of the spring 50. It is important to note, however, that ifthe heater is not in a functioning condition there is no way that theoperator will be able to create a dangerous condition inadvertently bycausing fuel to continue to flow to the heater since it will require hisconstant attention in depressing the button I22 every two minutes or so.

The heater is placed out of operation either by opening the heaterswitch 16 or by turning the vehicle ignition switch to the off position.As soon as this is done the shut-off valve 28 is de-energized, therebyinterrupting the supply of fuel to the heater. Since the heater is hotand since some fuel still remains therein, the circuit is so arrangedthat the combustion air blower motor I08 and the ventilating air blowermotor IIO receive energy directly from the battery by way of lead I94and contacts I02 and 94. The combustion air blower motor and theventilating air blower motor therefore continue in operation until allof the fuel has been burned away and until the heater has cooledsufficiently to shift the thermostatic igniter switch 92 to the startingposition, that is, with contact 94 against cohtact 96, after which bothblower motors are deenergized.

This device has very substantial advantages over the commonly usedarrangement wherein fuel is supplied to a heater and interruptedsubsequently if the heater does not start. One of these advantages isthat most systems of the conventional nature depend upon thecharacteristics of a time delay relay in order to time the startingperiod. These time delay relays are conventionally of the type wherein abimetallic member is heated by an electric resistance heater such thatafter the temperature of the bimetallic member has been raised to acertain predetermined point the switch will shift so as to interrupt thefuel supply to the heater.

These switches have several disadvantages, particularly in automotivevehicles. One of the most serious of these is that the voltagefluctuations in an automotive vehicle electrical system are considerablewith the result that the electric energy the resistance heater receivesmay vary so greatly under different conditions as to make it extremelydifiicult and expensive to provide a time delay switch which will have asumciently long period of delay under high voltage conditions and asufficiently short period of delay under low voltage conditions. Inotherwords, it is expensive to provide a switch designed to operate in twominutes under high voltage conditions and which will also operate underlow voltage conditions, since under the latter condi- 7 tions the heatloss of the thermostat may balance the heat gain at a temperature belowthat at which the switch is designed to operate.

The present system, however, overcomes this and other disadvantagesbecause it does not attempt to provide a time limit during which aheater is supplied with fuel for starting purposes, but rather isolatesand provides only a certain predetermined quantity of fuel which is usedfor this purpose. It is also apparent that the device is not sensitiveto vibratory forces or to orientation since the diaphragm 38 hasextremely low mass and therefore produces only low forces as compared tothe hydraulic pressure acting upon the two sides thereof.

The circuit of Fig. 5 which accomplishes generally the same result asthe circuit of l' ig. 4 includes the electric lead I24 which, as in theprevious instance, is connected to the vehicle ignition switch so thatthis lead is energized whenever the iginition is in the on position.This lead is connected through a single pole, single throw heater switchI26 and a thermostatic overheat switch I28 to the fuel shut-off valve28. The output side of the heater switch is also connected through abranch lead I30 to one of the fixed contacts I32 of a double pole,double throw switch I34 preferably of the snap action type. The twomovable contacts I36 and I38 of this switch are connected together by alead I40 also connected tcrthe combustion air blower motor I08. theother side of which is grounded.

The switch I34 is of the thermostatic type and is associated with theheater in the same manner as igniter switch 92 in the previousembodiment. The contacts of this switch are so arranged that when theswitch is cold one of the movable contacts is associated with thepreviously referred to fixed contact I32 while the other movable contactI30 is in engagement with fixed contact I42 connected to the igniterI00, the other side of which is grounded. When the temperature of thethermostatic switch I34 has been raised sufiiciently to indicate thatthe heater is in operation the movable contacts I36 and I38 snap intoengagement with the fixed contacts I44 and I46, respectively. Of these,the contact I44 is connected directly to the vehicle battery and also toone side of a normally open reset switch I48, the other contact of whichis connected to the other fixed contact I 46 of switch I34 and also tothe ventilating air blower motor H and the by-pass safety valve 60.

The reset switch I48 may be considered as essentially similar to thereset switch II4 excepting that it is a normally open single pole,single throw switch spring loaded to the open position instead of beinga double throw switch.

- The circuit of Fig. operates in the following manner. Assuming thatthe heater is cold and that the lower chamber 40 of the valve in Figs. 2and 3 is filled with fuel, if now the vehicle ignition switch is shiftedto the on" position and the heater switch I26 is closed, current willflow through the thermostatic overheat switch I28 to the shut-off valve28, thereby opening the same so as to permit fuel to flow to the heaterfrom the chamber 40. Simultaneously current flows through the branchlead I to the contact I32 and thence by way of contacts I36 and I38 tocontact I42 and to the igniter I00. Also it energizes the combustion airblower motor I08 through lead I 40. Inasmuch as the igniter quicklyheats to ignition temperature under these conditions and sincecombustion air and fuel are ill being supplied, the heater will normallystart after a brief interval.

When the heater has been in operation for a matter of a half minute orso the thermostatic switch I34 will heat sufllciently to shift thecontacts I36 and I38 from contacts I32 and I42 to contacts I44 and I46.Since contact I44 is connected directly to the battery it will be seenthat when this switch shifts, the combustion air blower will beenergized directly from the battery rather than through the heaterswitch I26 and that the ventilating air blower motor H0 and the by-passsafety valve will be energized by way of contacts I44, I36, I38 and I46in that order.

Since the by-pass safety valve 60 has now been energized and opened, theheater continues to receive fuel and the diaphragm moves upwardly so asto refill the chamber 40.

In the event that the heater does not start, the fuel within the chamber40 becomes exhausted in about two minutes or so. After the heater hasbeen repaired pushing the reset button of the switch I48 opens theby-pass safety valve .and permits the lower chamber 40 to be refilled.

It will be seen that the circuit of Fig. 5 operates in a manneressentially similar to that of Fig. 4, excepting that it uses somewhatdifferent although standard switch components and has the advantage ofkeeping the ventilating air blower motor out of operation untilcombustion has become well established in the heater. In other words,the ventilating air blower motor is turned on at the same time that theigniter is de-energized. The advantage of this is that no coldventilating air is circulated during the warm-up period of the heater;As in the previous example, placing the heater out of operation byopening either the heater switch or the engine ignition switchde-energizes only the fuel shut-off valve 28, thereby permitting theventilating air blower motor and the combustion air blower motor tocontinue in operation until all remaining fuel has been burned and theheater has been cooled.

The circuit of Fig. 6 is similar to that of Fig. 4 excepting that arelay is used to handle the heavier currents required by the igniter andthe blower motor. In this circuit the main lead I50 extending from thevehicle ignition switch is connected to the heater switch I52 and thenceby way of lead I54 and branch lead I56 through the single pole, singlethrow normally closed thermostatic overheat switch I58 to the fuelshut-off valve 28. Lead I54 is also connected to the coil I60 of a relayI62, the other side of the coil being grounded. Thus, when the heaterswitch is closed and when the vehicle ignition switch is in the on"position the fuel valve 28 is energized and opened and the coil I60 ofthe relay I62 is energized. This relay is of the normally open singlepole, single throw type and has contacts I64 which are closed when thecoil I60 is energized. One of the contacts I64 is connected directly tothe vehicle battery while the other is connected to ground through ablower motor I66. Although a single blower motor is shown it will beassumed that it will supply both ventilating and combustion air to theheater. If desired, two motors wired in parallel may be used in themanner illustrated in Fig. 4.

The contact I64 connected to the blower motor I66 is also connected by alead I68 to the swinging member I10 of a thermostatic igniter switchI12. This switch is of the single pole, double throw type and is soarranged that the swing ing contact 0 is in engagement with a contactI14 connected to the igniter I when the igniter switch is cold whereasthe swinging contact I engages contact I16 connected by a lead I18directly to the battery when the igniter switch is hot.

The lead I68 is also connected by a branch I80 to one end of the coil ofthe by-pass safety valve 60, the other end of whichis connected to theswinging contact member I82 of a reset switch I84. This switch is of thesingle pole,

double throw spring loaded type, in other words. the type shown in Fig.4. and is arranged so that the contact I82 is normally spring loadedinto engagement with a fixed contact I86 connected by a branch I88 tothe fixed contact I14 of the thermostatic igniter switch I12. The otherfixed contact I90 of the reset switch is connected to ground and engagesthe swinging contact I82 only when the reset button I92 is pushed andheld.

When this circuit is used, closure of the vehicle ignition switch andthe heater switch I52 supplies electrical energy through the overheatswitch I58 to the fuel shut-off valve 28, thus opening the connectionbetween valve chamber and the heater. Simultaneously relay coil I60 isenergized, thereby causing relay contacts I64 to close so that energy issupplied directly from the battery by way of switch contacts I64 to theblower motor I66and by way of switch I12 to the igniter I00. The by-passsafety valve 60 is not energized, however, since both ends of its coilare connected to points in the circuit at the same potential. In otherwords, the by-pass safety valve is connected across contacts I10 and I14which are closed.

After the heater starts, the igniter switch I12 shifts to bring contactI10 against contact I16. This causes electrical energy to be suppliedfrom the battery by way of lead I18 to contacts I16 and I10 and thenceto the blower motor I66, so that the blower motor is no longer directlyunder influence of the relay I62. Also, current will now fiow by way ofthe lead I18, contacts I16 and I10, lead I68, branch I80 through thecoil of the valve 60 and thence through contacts I82 and I86 and leadI88 to ground through the igniter I00. Thus, the by-pass valve is openedso as to permit a continuing supply of fuel to the heater and to permitthe chamber 40 to refill.

In the event that the heater does not start, the fuel will be exhaustedas in the previous examples and similarly also the fuel chamber 40 maybe refilled by pushing and holding the reset button I92. Similarly,also, the blower motor will continue in operation after the heaterswitch or the ignition switch has been opened since opening of thislatter portion of the circuit only deenergizes the fuel valve 28, theblower motor continuing to receive energy until the igniter switchcools.

The circuit of Fig. 7 uses a relay much like the circuit of Fig. 6 toaccomplish much the same results as the circuit of Fig. 5. In thisarrangement a double pole, double throw relay I94 has one end of itscoil I96 connected by a lead I98 directly to the vehicle battery. Theother end of the coil I96 is connected by way of a lead 200 to theswinging contact 202 of a single pole, double throw reset switch of thepush button type such as is used in the circuits of Fig. 4 and Fig. 6.

The contact 204 with which contact 202 normally is in engagement isconnected through a normally open single pole, single throw thermostaticigniter switch 206 to ground. This igniter switch is open when cold andcloses whenever the temperature of the heater rises sufliciently toindicate that efflcient combustion is taking place. The normally opencontact 208 of the push button reset switch is-connected to ground. Itis apparent, therefore, that the relay coil I96 is energized only afterthe igniter switch 2.06 has closed following a period of heateroperation.

The moving contacts 2I0 andp2l2 of relay I94 are normally in engagementwith fixed contacts H4 and 216 respectively. (if these, contact 2I4 isconnected by a lead 2 I8 to one side of a normally open single pole,single throw heater switch 220, the other end of which is connected tolead 222 leading to the vehicle ignition switch. Lead 2I8 is alsoconnected by way of a branch 224 to one side of a normally closed singlepole, single throw thermostatic overheat switch 226, the other terminalof which is connectedto ground through the fuel shut-off valve 28.

The moving contacts 2I0 and 2.I2 of the relay I94 are connected togetherand are also connected by a lead 228 to the combustion air blower motorI08, the other terminal of which is grounded. The other normally closedcontact'2l6 of relay I94 is connected to ground by way of theigniterI00. 0f the normally open contacts of the relay I94, one, indicated bythe numeral 230, is connected to the"'lead I98 extending directly to thebattery while the other of these contacts, 232, is connected to theby-pass safety valve 60 and the ventilating air, blower motor H0 inparallel.

When the ignition switch and heater switch 220 are closed, energy issupplied through lead 224 and switch 226 to the fuel shut-off valve 28so as to connect the fuel chamber 40 to the heater, thereby permittingfuel to be supplied to the heater from the chamber. Simultaneously,energy is supplied through branch lead 2I8 and contacts 2I4 and 2I0 tolead 228, thereby energizing the combustion air blower motor. Also.since contacts 2I2 and 2I6 are in engagement, the igniter is energized.

After the heater has been in operation for a brief interval the igniterswitch 206 closes, thereby energizing the relay coil I96 by way ofbattery lead I98, relay coil I96, lead 200, switch contacts 202 and 204,and switch 206 and thence to ground. Energization of the relay coil I96shifts contacts 2I0 and M2 into engagement with contacts 230 and 232respectively. Since contact 230 is connected directly to the vehiclebattery, it will be seen that the combustion air blower motor I08 nowreceives energy independently of the heater switch 220. Also, theigniter will be tie-energized and current will fiow from the batterylead I98 through contacts 230 and 2I0 to contact 2 I2 and thence by wayof contact 232 to the by-pass safety valve and the ventilating airblower motor.

If the heater does not start promptly and the fuel in the chamber 40becomes exhausted it may be replenished by manually holding the resetpush button of the switch 202 which energizes the relay I96independently of the igniter switch 206. This circuit operates much inthe manner of the circuit of Fig. 5 in that although both the combustionair blower motor and the ventilating air blower motor remain energizedafter the heater has been turned off until all remaining fuel has beenburned and the heater has been cooled sufficiently to cause operation ofthe igniter switch 206, the ventilating air blower motor does not comeinto operation during the starting cycle until the heater is hot. Inother words, cold ventilating air is not circulated during the warm-upperiod.

If it is desired to use a system of this type with in severalmodifications thereof it is contemi plated that still othermodifications may be made without departing from the spirit of myinvention. It is understood, therefore, that the invention is to bemeasured by the scope of the following claims.

I claim:

1. A fuel safety device comprising a flexible diaphragm, means enclosingone side of said diaphragm to form a chamber with said diaphragm formingone wall thereof, means enclosing the other side of said diaphragm toform a second' chamber with said diaphragm forming one wall thereof sothat when said diaphragm is displaced in one direction, said firstchamber is enlarged in volume while the volume of the second chamber isreduced and when said diaphragm is displaced in the opposite directionthe volume of the first chamber is reduced while the volume of thesecond chamber is enlarged, means forming a fuel supply connection tosaid first chamber, means forming a fuel outlet connection from saidsecond chamber, resilient means for urging said diaphragm in thedirection for reducing the volume of said first chamber, means providingan outlet connection for said first chamber in direct communication withthe outlet to said second chamber, and valve means for controlling theflow through the outlet connection for said first chamber.

2. A fuel safety device comprising a movable member, means enclosing oneside of said movable member to form a chamber with said movable memberforming one wall thereof, means enclosing the other side of said movablemember to form a second chamber with said movable member forming onewall thereof so that when said movable member is displaced in onedirection said first chamber is enlarged in volume while the volume ofthe second chamber is reduced and when said movable member is displacedin the opposite direction the volume'of the first chamber is reducedwhile the volume of the second chamber is enlarged, means forming a fuelsupply connection to said first chamber, means forming a fuel outletconnection from said second chamber, resilient means tending to movesaid movable member in the direction for reducing the volume of saidfirst chamber, means providing an outlet connection for said firstchamber in direct communication with the outlet to said second chamber,and valve means for controlling the flow through the outlet connectionfor said first chamber.

3. A fuel safety system for use with a combustion heater comprising, aflame detector switch responsive to combustion in the heater, a flexiblediaphragm, means enclosing one side of said diaphragm to form a chamberwith said diaphragm forming one wall thereof, means enclosing the otherside of said diaphragm to form a second chamber with said diaphragmforming one wall thereof so that when said diaphragm is displaced in onedirection said first chamber is enlarged in volume while the volume ofthe second chamber is reduced and when said diaphragm is displaced inthe opposite direction the volume of the first chamber is reduced whilethe volume of the second chamber is enlarged, means for supplying fuelunder pressure to said first chamber, means forming a connection fromsaid second chamber to the heater, resilient means for urging saiddiaphragm in the direction for reducing the volume of said firstchamber, means providing a fluid connection between said chambers, anormally closed magnetic valve arranged for controlling the fiow throughsaid last connection, and electric circuit means including said flamedetector switch adapted for opening said valve when said flame detectorresponds to combustion in said heater.

4. A fuel safety system for use with a combustion heater comprising, aflame detector switch responsive to combustion in the heater, a movablemember, means enclosing one side of said movable member to form achamber with said movable member forming one wall thereof, meansenclosing the other side of said movable member to form a second chamberwith said movable member forming one wall thereof so that when saidmovable member is displaced in one direction said first chamber isenlarged in volume while the volume of the second chamber is reduced andwhen said movable member is displaced in the opposite direction thevolume of the first chamber is reduced while the volume of the secondchamber is enlarged, means for supplying fuel under pressure to saidfirst chamber, means forming a connection from said second chamber tothe heater, resilient means for urging said movable means in thedirection for reducing the volume of said first chamber, means providinga fluid connection between said chambers, a normally closed magneticvalve arranged for controlling the fiow through said last connection,and electric circuit means including said flame detector switch adaptedfor opening said valve when said flame detector responds to combustionin said heater.

5. A fuel safety device comprising, means providing a first expansiblechamber, means providing a second expansible chamber, both of said meansbeing arranged so that collapse of one of said chambers causes expansionof the other of said chambers, resilient means for expanding the secondof said chambers, means forming a fluid fuel supply connection to saidfirst chamber, means forming a fuel outlet connection from said secondchamber, means providing an outlet connection for said first chamber indirect communication with the outlet to said second chamber, and valvemeans for controlling the flow through the outlet for said firstchamber.

6. A fuel safety system for use with a combustion heater comprising, aflame detector switch responsive to combustion in the heater, meansproviding a first expansible chamber, means providing a secondexpansible chamber, both of said means being arranged so that collapseof one of said chambers causes expansion of the other of said chambers,means normally expanding the second of said chambers, means forsupplying fluid fuel under pressure to said first chamber, means forminga fuel outlet connection from said second chamber to said heater, meansproviding a fluid connection between said chambers, a normally closedmagnetic valve arranged for controlling the flow through the last saidconnection, and electric circuit means including saidfiame detectorswitch adapted for openingsaid valve when said flame detector re-'providing a first expansible chamber, means pro-- viding a secondexpansible chamber, both of said means being arranged so that collapseof one of said chambers causes expansion of the, other of said chambers,means normally expanding the second of said chambers, means forsupplying fluid fuel under pressure to said first chamber, means forminga fuel outlet connection from said second chamber to said heater, meansproviding a fluid connection between said chambers, a normally closedmagnetic valve arranged for controlling the flow through the last saidconnection. electric circuit means including said flame detector switchadapted for opening said valve when said flame-detector responds tocombustion in said heater, a normally closed magnetic valve arranged insaid fuel outlet connection, and an electric circuit for opening thelast said valve to permit operation of said heater.

8. A fuel safety system for use with a fluid fuel burning combustionheater comprising, a source of fluid fuel under pressure, fluid motormeans including means defining a collapsible chamber for isolating apredetermined quantity of fuel, hydraulic means for collapsing saidchamber to feed the fuel isolated thereby to said heater, resilientmeans normally tending to expand said chamber, a first conduit formingmeans for conveying fuel from said chamber to said heater, a secondconduit forming means through which said hydraulic means is subjected tothe hydraulic pressure of the fuel at said source connecting said sourceof fuel to said hydraulic means, a third conduit forming means forsubjecting the interior of said isolating chamber to the hydraulicpressure of the fuel at said source to neutralize the effect in saidhydraulic means of the pressure of the fuel at the source, and a valvefor closing communication through said third conduit forming means.

9. In a device of the class described the combination comprising meansforming a hollow casing having internal walls defining a closed space,means forming a flexible wall in said casing dividing said closed spaceinto first and second fluidtight chambers, means biasing said flexiblewall to a predetermined position when balanced hydraulic pressures areexerted on opposite sides thereof, means forming an inlet to the firstchamber for delivering fluid under pressure thereto from an externalsource, means forming an out let connection in direct communication withboth chambers, and valve means in said outlet connection to closecommunication between the said first chamber and outlet connection.

10. In a device of the class described the combination comprising meansforming a hollow casing having internal walls defining a closed space,flexible means cooperating with the walls of said casing to definefluid-tight chambers increasing or decreasing in volume in accordancewith movements of said flexible means, biasing means to move saidflexible means to a position at which said chambers have a predeterminedvolume, means forming an inlet connection for delivering fluid underpressure to said first chamber from an external source, means forming anoutlet for conveying fluid from said device to the exterior, passagewayforming means connecting said two chambers to each other for equalizingthe pressure,. therein and to said outlet, and valve means to controlflow of fluid between said chambers independently of the control of flowfrom the second chamber to the outlet.

11;; In a device of the class described the combination comprising meansforming a hollow casing having internal walls defining a closed space,flexible means cooperating with the walls of said casing to definefluid-tight chambers increasing or decreasing in volume in accordancewith movements of said flexible means, means for biasing said flexiblemeans to a position at which said chambers have a predeterminedvolume,,means forming an inlet connection for delivering fluid underpressure to said first chamber from an external source, means forming apassageway between said chambers for equalizing the pressure of thefluid therein, means forming an outlet connection for conveying fluidfrom said second chamber to the exterior of said device, and a valve toclose communication through the passageway between said first and secondchambers.

12. A fuel safety system for use with a fluid fuel burning heatercomprising, a flame detector switch responsive to combustion in theheater, means providing first and second expansible chambers arranged sothat collapse'of one of said chambers causes expansion of the other ofsaid chambers, biasing means to collapse said first chamber, means forsupplying fluid fuel under pressure to said first chamber, means forminga fuel outlet connection from said second chamber to said heater, meansproviding a fluid connection between said chambers, a normally closedmagnetically operated valve arranged for controlling the flow throughthe last said connection, electric circuit means including said flamedetector switch adapted for opening said valve when said flame detectorresponds to combustion in said heater, power operated combustion andventilating air supply means and circuits for energizing said poweroperated air supply means including a circuit independent of said flamedetector switch for energizing said air supply means" before said flamedetector switch responds to combustion, and a circuit including saidflame detector switch for energizing said air supply means when saidflame detector responds to combustion in said heater.

13. A fuel safety system for use with a fluid fuel burning heatercomprising, a flame detector switch movable from one position to anotherin response to combustion in the heater, means providing first andsecond expansible chambers arranged so that collapse of one of saidchambers causes expansion of the other of said chambers, biasing meansto collapse said first chamber, means for supplying fluid fuel underpressure to said first chamber, means forming a fuel outlet connectionfrom said second chamber to said heater, means providing afluid'connection between said chambers, a normally closed magneticallyoperated valve arranged for controlling the flow through the last saidconnection, electric circuit means including said flame detector switchadapted for opening said valve when said flame detector responds tocombustion in said heater, independent combustion and ventilating airsupply means, independent circuit means connected to said flame detectorswitch for connecting said combustion and ventilating air supply meansto a source of electric current including a circuit to connect saidcombustion air supply'means to said source of current at both positionsof said flame detector switch, and a circuitito connect said van- 3 15tilatlng air supply means to a source of current when said flamedetector switch responds to combustion in said heater.

. GEORGE W. ALLEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 941,587 Putnam NOV. 30, 1909 NumberNumber

